The present invention generally pertains to two fields of endeavor: memory devices and photonics. More particularly, the present invention pertains to ferroelectric memory cells that store information in the direction of polarization of a ferroelectric film, and secondly, electronic or photonic devices that source, detect, modify, and control light.
The civilized world has a great need to store information for one purpose or another, and all of the information is stored in memory devices of one form or another. Supercomputers, cloud storage infrastructure, personal computers, mobile phones and more all require memory to function. Each application generally requires memory that is specifically designed for it. That is, server farms require low cost high-density memory, mobile devices require low power memory, and supercomputers require high speed memory. Currently, different memory devices are used for each of the applications in order to better meet the needs of the application. A memory device containing the memory cells presented in this patent has the characteristics to potentially replace many forms of existing memory because it is non-volatile (Information is saved even when the power is turned off), have high memory density, high speed, good reliability, and low power usage.
Some aspects of the current invention are unrelated to any prior art that could be found. However, the use of a ferroelectric memory element in conjunction with a single Schottky barrier is known in the art and is disclosed, for example, in U.S. Pat. No. 5,512,773 of Wolf et al. The Wolf patent is believed to indicate the general state of the art and to contain a discussion of the general theory of operation of such a memory element.
Parts of this invention also pertain to photonic devices. For many years, ferroelectric materials have been used extensively in various photonic devices including, optoelectronic modulators, terahertz wave generation, spectroscopy, and tunable phase arrays. However, many ferroelectric materials, including lithium niobate, have proven difficult to properly manufacture on the nano-scale. This has slowed innovation in this field and made it difficult to create integrated photonic circuits. This invention solves this problem by presenting a method for depositing well-textured lithium niobate on the nano-scale.
Methods for depositing lithium niobate by RF sputtering is known in the art and is disclosed, for example, in U.S. Pat. No. 3,649,501 to Sadagopan et al. The Sadagopan patent is believed to indicate the general state of the art.